The present invention relates to a method and/or system for the alkylation of an olefin with an isoparaffin utilizing an acidic catalyst mixture. In another aspect, this invention relates to a method of increasing the isoparaffin to olefin ratio in the alkylation reactor section in order to reduce the amount of isopentane made in the reaction of isobutane with olefin.
The use of catalytic alkylation processes to produce branched hydrocarbons having properties that are suitable for use as gasoline blending components is well known in the art. Generally, the alkylation of olefins by saturated hydrocarbons, such as isoparaffins, is accomplished by contacting the reactants with an acid catalyst to form a reaction mixture, settling the reaction mixture to separate the catalyst from the hydrocarbons, thereby forming a catalyst mixture phase and an alkylation reactor effluent. The alkylation reactor effluent is further separated, for example, by fractionation, to recover the separate product streams. Normally, the alkylation reactor effluent of the alkylation process contains hydrocarbons having five to ten carbon atoms per molecule. In order to have the highest quality gasoline blending stock, it is preferred for the alkylate hydrocarbons formed in the alkylation process to be highly branched and contain seven to nine carbon atoms per molecule.
It has long been known that increasing the isobutane to olefin ratio in an alkylation reactor is beneficial to alkylate product quality. Many alkylation unit operators run their downstream hydrocarbon fractionation sections at or near their full capacity, and thus, are constrained from recycling additional isobutane to the alkylation reactor section. Therefore, development of an improved process and/or system for increasing the isobutane to olefin ratio in an alkylation reactor without increasing the capacity load on the fractionation system would be a significant contribution to the art.